his study investigates homogenized elasto-viscoplastic material modeling of thick perforated plates operating at high temperatures. To this end, homogenized stress-strain relations of a periodic unit cell of thick perforated plates subjected to simple and complex loading are analyzed using a homogenization method of periodic solids. The resulting homogenized stress-strain relations are then simulated using a recently developed elasto-viscoplastic macro-material model based on a general form of quadratic equivalent stress. It is shown that this macro-model successfully represents the macro-anisotropy and macro-volumetric compressibility revealed in the homogenization analysis.

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In this study, the distributions of microscopic stresses at a free edge of a cross-ply carbon fiber-reinforced plastic (CFRP) laminate are analyzed three-dimensionally based on a homogenization theory. For this, the mathematical homogenization theory for elastic materials is reconstructed for CFRP laminates with free edges using a traction free boundary condition. This theory is then applied to the analysis of microscopic stress distributions at a free edge of a cross-ply CFRP laminate subjected to in-plane uniaxial tension. It is shown that microscopic in-plane shear stresses noticeably occur at the interlaminar area between 0 ° - and 90 ° - plies, especially around the free edge.

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In carbon nanotube/ceramics composites, the clarification of the interfacial properties between carbon nanotube (CNT) and ceramics matrix is crucial for its applications. The pull-out process of a CNT from an alumina (α-Al_2O_3) matrix is investigated for the first time by using molecular mechanics (MM) simulations to study these interfacial properties due to van der Waals (vdW) and electrostatic Coulombic interactions. The pull-out force of carbon nanotube is found to be proportional to its diameter, and independent of nanotube length and alumina grain boundary type. The interfacial shear stress during the pull-out process is further systematically explored to address this phenomenon. Moreover, the pull-out process of a multi-walled carbon nanotube is simulated to study the influence of wall number on the pull-out force.

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In order to clarify degradation mechanisms of Ni-base superalloy under creep or fatigue condition, the mechanism of the directional coarsening of y' phases (rafting) under uni-axial strain was analyzed by molecular dynamics (MD) analysis. Stress-induced anisotropic diffusion of Ni and Al atoms in γ' phases perpendicular to the interface was observed around the simulated γ/γ' interface structure. Therefore, reduction of strain-induced anisotropic diffusion is effective for decreasing the evolution of the rafting and improving the creep or fatigue resistance of the Ni-base superalloy.

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The authors developed the finite element method (FEM) for micropolar elastic solids and applied it to the problem of topology optimization. The weighted residual method and 8-node isoparameteric elements were employed for the FEM analysis. The solid isotropic material with penalization (SIMP) method and the gravity control function were employed in the optimization procedure. To test the numerical solutions, the bending problem of the cantilever was used. In this analysis, the effects of the engineering material constants for micropolar elasticity, the coupling number N, which is related to stresses, and the characteristic length 1, which is related to couple stresses, are researched. The optimal structures of micropolar materials are strongly influenced by material properties of bending. Though the optimal topologies of classical elastic solids are truss frames, in general, those of micropolar materials are rigid frames. Since the checkerboard structures are more apt to appear in the optimization process for micropolar solids than in classical elasticity, filtering (the gravity control function employed in this paper) or other techniques are required to obtain practical solutions. The proposed method could potentially solve the optimization problems of biomaterials such as bone tissue.

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In this study, a MDS specimen which a uniform distribution of shear stress can be realized by using comparatively simple testing device is studied for impact shear deformation of TRIP steel. The shape and size of the specimen for an appropriate measurement of its impact shear deformation are determined by FEM. Then, a rate sensitivity on shear deformation of TRIP steel is investigated by measurement of shear deformation at various strain rate using a conventional material testing machine and the split Hopkinson pressure bar method.

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In order to evaluate a strain rate sensitivity of a dynamic flow stress of FCC metal at very high strain rates, very high strain rate tests are conducted for aluminum at temperatures of 290, 373, and 473K in the strain rate range from about 1×10^3_s^<-1> to 2×10^4_s^<-1>. The flow stress increases steeply above about 5×10^3_s^<-1>. The behavior is interpreted on the basis of a simplified model which can represent a transition in the rate controlling mechanism of dislocation motion from a thermally activated process to a viscous drag. By taking the temperature and stress dependence of the moving dislocation density into consideration, a good agreement between the calculated and measured flow stress is obtained.

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Work hardening character of polycrystalline material is studied by using a discrete dislocation plasticity. Grain boundaries are modeled as barriers. Grain size dependences of yield stress and work hardening factor are investigated for model of different grain size, and the result is compared with that of single crystal model. Dislocation pile-up is observed and it is shown that the work hardening property is more significant in fine grain model.

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Polycarbonate was a material which had the highest impact strength in the high polymer materials. However, there was a problem that impact strength decreased in a low-temperature environment. So, in this study, change of impact strength was inspection about PC that copolymerized of the Polydimethylsiloxane that was an elastic comonomer. As a result, it found out that PDMS-PC was preserving the fracture behavior of a ductility state at 243K , and had controlled reduction of fracture energy.

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Generally, reinforcement clusters are formed in a composite. Some of reinforcements in the cluster may break under an applied load when the rapture strain of the reinforcement is smaller than that of the matrix. As a result, the broken and the unbroken reinforcements coexist within the cluster. The multi-phase triple inclusion model is developed to analyze such a composite and effect of the degree of clustering of the reinforcement on the stiffness reduction of such a composite is estimate numerically.

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Carbon nanotubes are nano-scale fibers that have high specific elastic modulus and tensile strength. The potential as reinforcement materials for polymers has, however, not been realized so far. In this study, two types of carbon nanotube preforms, unidirectional sheet and spun yarn, were used to achieve high efficiency of reinforcement. Composite specimens were fabricated using epoxy resin, and tensile tests were conducted for investigating tensile properties. The experimental results showed that using carbon nanotube preforms is effective for achieving high mechanical properties.

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This study analyzed impact damage and tension after impact (TAI) strength of a carbon fiber-reinforced sheet molding compound (CF-SMC). First, low-velocity impact damage was introduced to CF-SMC coupon specimens for a variety of impact energies. Next, the impact damage was observed by ultrasonic inspection and optical microscopy to determine the damage state and quantify the damage area and depth. Then, TAI strength was measured and correlated with such parameters as maximum impact load, impact energy, and damage area and depth. Finally, a simple fracture-mechanics model for predicting TAI strength was proposed.

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CFRP laminates are used by about 50% weight ratio in the body of the Boeing 787 jet plane. Many kind of impact damage, for example due to the collision of small stone, bird, tool dropping and hail, may be introduced in the airplane body during the long time use. The effect of impact damage due to dropping weight on the flexural and tensile strength of the fabricated CFRP and GFRP laminates, were investigated. Both strength of CFRP decrease strongly depending on the impact damage, as compared with the results of GFRP. Effect of the cure condition on the both strength of CFRP and GFRP are small.

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Compressive strength of a unidirectional CFRP was estimated based on a model of column buckling on elastic foundation. It was shown that the compressive strength based on the column buckling model coincided with the compressive strength based on the fiber kinking model when high fiber volume fraction was supposed for the unidirectional CFRP. Apparent shear modulus of a carbon fiber in the in-phase buckling was calculated considering shear and bending deformation as an apparent shear deformation. Compressive strengths of unidirectional CFRPs were estimated by considering the apparent shear modulus. The estimation results on various types of unidirectional CFRP showed good agreement with the experimental results. Upper and lower limit of the compressive strengths of the unidirectional CFRPs were revealed theoretically.

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A procedure for constructing the anisomorphic constant fatigue life (CFL) diagram for composites on the basis of the static strengths in tension and compression and the reference S-N relationship for the critical stress ratio, which was developed in an earlier study, is further tested on a woven CFRP quasi-isotropic laminate at room and high temperatures. Constant amplitude fatigue tests were first performed at RT, 100 and 150℃ for different stress ratios to elucidate the effects of R-ratio and temperature on S-N relationship. Then, validity of the anisomorphic CFL diagram approach to prediction of the fatigue lives of the composite for cyclic loading at different stress ratios and test temperatures is evaluated by comparing the predicted and experimental results.

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To better understand the domain-switching characteristics of lead zirconate titanate (PZT) ceramics, the orientations of domains have been directly investigated during loading and unloading using various experimental techniques. Upon loading, linear and nonlinear fracture mechanics of the PZT ceramics are observed. The slope of the stress-strain response is attributed mainly to lattice strain and domain switching strain. During the loading process, electrical activity also occurs several times in the PZT ceramics. This electrogenerative event is caused by severe domain-switching. The characteristics of domain-switching and reverse switching are detected during the loading and unloading processes. The amount of domain-switching depends on the grain, due to different stress levels. Two patterns of 90° domain-switching systems are characterized, namely (i) 90° turn about the tetragonal c-axis and (ii) 90° rotation of the tetragonal a-axis.

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To better understand the material properties of PZT ceramics, fatigue tests have been carried out using a new testing system. This testing system produces cyclic loading with a wide range of fatigue frequencies: 1 Hz-72 kHz. The influence of fatigue frequency on the fatigue properties of a PZT ceramic has been investigated and it appeared that the fatigue strength is not linearly correlated with the fatigue frequency. The reason for this is due to the resonance caused by the oscillation. Thus, the fatigue frequency can change the severity of the sample vibration. The extent of sample vibration is associated with the sonar intensity from the ceramic, which is linearly related to the crack growth rate. The sonar intensity can be clearly observed using a condenser microphoneone. The details of the resonance fatigue properties have been systematically examined.

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This paper presented a multiscale simulation of piezoelectric materials. Microstructural features were investigated through EBSD measurement by using an amorphous osmium coating for the preventing charging. Realistic crystal orientations obtained from the EBSD measurement were introduced into multiscale finite element simulations based on homogenization theory to reveal the relationship between the macrostructure and the microstructure. First, a two-dimensional microstructural model was constructed and the effect of the sampling area of EBSD-measured crystal orientations was analyzed. Second, a three-dimensional microstructural model was constructed by the repetition of polishing and EBSD measurement and the influence of the microstructural thickness was investigated. We compared macrostructural homogenized material properties between two- and three-dimensional microstructures.

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This paper examines theoretically and experimentally the electromechanical behavior of multilayer piezo-actuators for fuel injectors at cryogenic temperatures. A thermodynamic model was employed to predict a monoclinic phase. A shift in the morphotropic phase boundary (MPB) between the tetragonal and rhombohedral/monoclinic phases with decreasing temperature was determined, and the temperature dependent piezoelectric coefficients were obtained. Temperature dependent coercive electric field was also predicted based on the domain wall energy. A finite element analysis was then performed to calculate the nonlinear electromechanical fields of the multilayer piezo-actuators from room to cryogenic temperatures, due to the polarization switching and shift in the MPB. In addition, experimental results on the electric field induced strain, which verify the model, were presented.

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Artificial hip joint which has been made of fiber reinforced plastics has advantages of high degree of freedom of the design parameters. Artificial hip joint consists of three parts, Cup, Head and Stem. In the artificial hip joint, the fixation of cup and pelvis is very important. Therefore, we made cups which have protuberances on surface and evaluated the mechanical characterization for the cups. In this study, the target is an evaluation of mechanical characterization for artificial joint cup considering various surface shapes, and the torsion-compression test and numerical analysis has been carried out for the estimation of fixed torque using a cup with different density of protuberance.

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In this study, the following were carried out for the purpose of the establishment of the strength evaluation technique of the pelvis: strain measurement by 3D digital image correlation method and nonlinear contact finite element analysis of the simulated bone. First, compression test using the cubic test piece of simulated bone was carried out for the identification of nonlinear mechanical properties. After that, compression test using the hip socket specimen was carried out, and it was compared with the analytical result of the hip socket model. The result showed that the strain distribution which is almost similar to the experiment was obtained.

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To investigate the effects of irradiation time and immersion period on mechanical properties of photo-cured dental composite resins, static compression tests were made for specimens with different preparation conditions. For the dependence on irradiation time, specimens were produced for irradiation time of t=15, 20, 30, 60, 90, 120 and 150 seconds. When the irradiation time increases up to t=90 s, density, Young's modulus and brittleness of specimens increase. On the other hand, for the dependence on immersion period, specimens were immersed in ion exchanged water at 37±1 degree C for 0, 30, 60 and 90 days. Young's modulus increases until 30 days while fracture strain decreases because interface between fillers and resin becomes weak due to the absorption of water.

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Considerable attention has been devoted recently to porous materials with light, high impact absorption, high thermal conductivity and biocompatible characteristics. We used a new method to fabricate salami-type porous metal from glass microcapsules and liquid metal. Each pore of its salami-like structure behaves as a micro-bell. This metal, which is more than 20% lighter than bulk material, also shows a unique characteristic: high-frequency oscillation is greatly attenuated when propagated in its medium. This method offers great potential for size, shape, and conformation control, with changed attenuation characteristics of its salami-like pore structure achieved merely by changing the mixing technique.

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In the present paper, some experimental testing and numerical simulations for thermal imprinting of glass-optical devices using finite element method were investigated. Thenno-viscoelastic property of the glass material was estimated using compression creep tests based on traditional thermo-viscoelastic theory. In this study, D263 was used as glass material. Glass thermal imprint tests were carried out with glassy carbon dies that were given to line & space or micro-lens array pattern machined by focused ion beam (NB). The optimum condition of imprinting temperature which given appropriate transcription profile of the glass was investigated. Moreover, numerical simulations for thermal imprinting of the glass were carried out by finite element method. Comparing experimental results with numerical ones, the transcription of height of groove or micro-lens obtained by experimental tests approximately agreed with numerical values.

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We have performed compressive simulation of triple-walled carbon nanotubes before and after the heat treatment by the molecular dynamics analysis using the adaptive intermolecular reactive empirical bond-order potential, and discussed a relationship between deformation and lattice defects in carbon nanotubes. This potential function can describe transitions between covalent bonding interactions and non-bonding ones. Many lattice defects and interlayer coupling are made by the heat treatment. The structure of inner and middle layer drastically changes in a model whose interlayer distances are smallest. Young's modulus under compression decreases by the heat treatment. Buckling stresses also decrease due to the presence of inhomogeneous structure of inner and middle layer.

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In this study, the elastic-viscoplastic properties of ultra-fine plate-fin structures with random laminate misalignment are investigated using the time-dependent homogenization theory in conjunction with the substructure method. For this, a unit cell of a plate-fin structure with randomly misaligned N layers is defined. The Y-periodic boundary condition is used on the side boundary surfaces of the unit cell. On the other hand, the boundary condition for periodic laminate misalignment proposed by the authors is applied on the top and bottom boundary surfaces. The unit cell is then divided into N substructures for applying the time-dependent homogenization theory combined with the substructure method to the elastic-viscoplastic analysis of the random plate-fin structure. Using the present method, elastic-viscoplastic behavior of ultra-fine plate-fin structures with randomly misaligned 10-100 layers is analyzed. It is shown that the random laminate misalignment can significantly affect the elastic-viscoplastic properties of plate-fin structures.

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Novel integrated process was developed to produce functionally-graded (FG) syntactic foams which have gradating distribution of Acrylonitrile hollow particles (micro-balloons) in epoxy matrix to absorb mechanical energy widely ranged from low to high stresses. By using floatation of the micro-balloons due to density difference between the matrix and the micro-balloons before curing matrix resin, the FG syntactic foams were fabricated by simple integrated process. Compression tests were conducted to evaluate local mechanical properties of the FG syntactic foams. Distributions of the mechanical properties in the FG syntactic foams were identified from the density distribution.

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In order to evaluate internal damage inside of carbon fiber reinforced plastic (CFRP) tubes by variation of thermal conductivity, a measurement device of thermal conductivity was developed from the viewpoint of measurement accuracy. The comparative static method was adopted as a measuring system for thermal conductivity, and the thermal conductivity was evaluated indirectly by the thermal conductivity of reference material in the method. In the present paper, CFRP tubes were subjected to impact loading, and the thermal conductivity was measured before and after the impact. The cross-section of CFRP tubes was also observed directly by optical microscope after the impact. As a result, the thermal conductivity was decreased by impact damage, and number of impact and number of impact points enlarge the decrease.

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The stitching yarn of NCF (Non Crimp Fabric) brings the improvement of out-of plane strength and the intricate microscopic structure. Although numerical method considering the microscopic structures based on the mesh superposition method has been proposed previously, the effects of the design parameters on damage development under bending load has not been investigated precisely. In this study, three points bending test under static loading have been carried out. The specimens are NCF composites consisted of four plies which stacking sequence has been [90/0]s, [0/90]s and the stitching patterns are promat and tricot. The effects of stitching yarn have been investigated by FE analysis based on the mesh superposition method. The results of the damage development of NCF under bending load have been described.

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The damage properties of fiber reinforced polymers (FRPs) emcompassing self-healing of interfacial debonding have been investigated numerically. Finite element analyses were performed using a three-dimensional model to predict the damage evolution in single edge notched tensile (SENT) specimens of unidirectional FRPs containing fiber strands coated with the self-healing polymer. Microcracking of the matrix and the coating layer was detected by the von Mises criterion. Maximum stress criterion was also used to evaluate breaking of the fiber strand. The effects of specimen thickness and coating properties on the damage properties are examined. Numerical results from the finite element analysis are compared with experimental data.

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The influence of the interlaminar interfaces on the longitudinal wave propagation behavior in a multilayered composite material immersed in water is investigated through FEM analysis. Spring boundary conditions are applied to each interface and different interfacial stiffnesses are considered by varying the spring constants. The results of amplitude reflection coefficient of the laminate are compared with those obtained by the transfer matrix method. Good agreement is observed between the results of FEM and the transfer matrix method. Reflection coefficient strongly depends on frequency. It is also found that there exists a stop band, a frequency range in which the reflection coefficient is near or equal to unity, and that this became wider as the interfacial stiffness decreases. From the short-time Fourier transform of waveform data, waves reflected by each interface are found to contain a frequency range corresponding to the stop band.

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A computational procedure for multiple scattering of elastic waves in unidirectional fiber-reinforced composite materials is presented. The present study deals with the time-harmonic propagation of the P wave (longitudinal wave) and the SV wave (shear wave polarized vertical to the fibers). The exciting and scattered fields for each fiber are expressed by the eigenfunction expansion, and a collocation method is used to determine the expansion coefficients numerically. With this procedure, the P and SV wave scattering and propagation in the unidirectional SiC/Ti-alloy composite are analyzed for a square arrangement of the fibers. This analysis enables to simulate multiple scattering considering mode conversion.

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Dental resin composites have been widely used in clinical, because of its operability and sensuousness. Since the resin composite is subject to cyclic stress in the oral environment, an understanding of the fatigue strength of these materials is needed to use with keeping safety. In this study, three-point bending fatigue tests of resin composites with several filler blend ratios were conducted to investigate the effect of filler size and filler content on fatigue strength. In order to consider an environmental property of the resin composite, the fatigue strength was also investigated in ethanol solution.

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This paper describes evaluation process of residual strengths of plasma-sprayed hydroxyapatite(HAp) coatings by Raman spectroscopy. Plasma-sprayed HAp coatings are widely used in the fields of medical implant in order to improve the biocompatibility of substrate alloys in vivo. The strength of the HAp coating is affected by complex factors. One of them is residual stresses that lead to cracking due to its positive value. The thickness of coatings limit methods of residual stress evaluations by using XRD etc and crystal phase is also changed during spraying, which disturb the accurate prediction of residual stress from macroscopic method. The authors then used Raman microscopy to observe residual stress distributions through the coatings. The peak value of Raman shift is moved in the case of plasma-sprayed one compared with bulk sintered one. Residual stress becomes lower in the edge of HAp coatings by cracking. In the cases of HAp coating and HAp+ Ti bond coat, residual stress became lower and no crack was observed. This result can explain the enhancement effect of bond coat on the strength of coatings.

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Recently, there have been efforts aimed at the repair and regeneration of damaged articular cartilage using tissue engineering. In tissue engineering therapy, cells are cultured in vitro to create a three dimensional (3-D) tissue designed to replace the damaged cartilage. Although the tissue engineering is a useful approach to regenerate cartilage, the mechanical property of the regenerated cartilage is not sufficient to replace natural cartilage. The purpose of this study is to create mechanically anisotropic cartilage using 3-D cell pattering technology. An anisotropic cartilaginous tissue was developed by cell patterning within hydrogel slabs using dielectrophoretic (DEP) forces. Tensile tests were performed to evaluate the material anisotropy. From the results of experiments the reconstructed tissue showed mechanical anisotropy in the tensile direction.

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A new cell culture module in an automatic culture system was developed. The proliferation of L929 fibroblast in cell culture by using the developed module was investigated. Cell culture tests in the developed module and the tissue culture flask were carried out with L929 fibroblast through 6, 24 and 48hours. This result showed that cell culture by using the developed module was possible. Cell proliferation in the developed module was as high as that in the tissue culture flask.

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In addition with medical materials, those involving cells are applied for tissue engineering recently. Cells involved in those medical materials experience physical dynamics after implantations. If the medical material exhibits high elasticity, cells would experience soft physical dynamics. However, if the medical material exhibits low elasticity, cells would experience hard physical dynamics. Medical materials with low elasticity are targeted to be used for high bio-compatibility and bio-absorbability. However, it is obscure whether cells on those medical materials with low elasticity could bear the hard physical dynamics after implantations. In this study, cells spread on soft material were stretched to investigate whether those cells could conserve physical structure even after the stretch. To evaluate conservation of the physical structure, stress fibers are visualized with GFP-actin. Furthermore, traction force was compared before and after the stretch.

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Many studies have focused on the fabrication of copper nanowires, because of their potential applications such as gene delivery. We successfully fabricated copper nanowires by electrochemical deposition method. Cu nanowires was synthesized by electroplating from a 0.4M CuSO_4 bath, the current was 0.005A.The length of nanowires can be controlled via deposition time and current. The length and the diameter of the nanowires are approximately 10 μm and 200nm respectively after depositing for 60 minutes. Nanowires with concentration of 10^2, 10^3, 10^4, and 10^5 were added to 96-well cell culture plate in which mesenchymal stem cells were pre-seeded. After incubating for 2 days, cytotoxicity of nanowires was measured with MIT assay method. Results indicated that cytotoxicity increased as the increase of nanowires density. Cell viability is approximately 80 % at the density of 10^5 compared with the control group, and at a lower density (10^2), mesenchymal stem cells were almost unaffected.

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Tailor-made tricalcium phosphate bone implants used in clinical trial were fabricated using a 3D ink-jet printer. Because the Tailor-made tricalcium phosphate bone implants have very poor mechanical properties such as stiffness & fracture strength, reinforcement are needed for many implant cases under loading. In this study, sintered α-TCP using molding injection molding method was interested. Influences of different volume fractions between tricalcium phosphate and binder on the material properties of sintered α-TCP are investigated through specimen samples molding. Mass density and SEM observation results are reported here and other mechanical comparison on bending elastic stiffness or else will be executed and reported in the future study.

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K_I-V curve of alumina was obtained by crack length measurement method using thin metal film for indentation small crack. Also a rising R-curve could be obtained from stable crack growth by three point bend with the 0.025 mm/min for the small crack. Results of fatigue tests showed a clear difference between the static and cyclic lifetimes. The life time prediction for cyclic load obtained by assuming that the rising R-curve behavior due to the crack tip closure disappeared by the cyclic load could well explain the experiments.

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Lead-free piezoelectric materials are becoming increasingly important for actuators and sensors. In this study, we investigated novel biocompatible lead-free piezoelectric materials in perovskite-type oxide A^<2+>B^<4+>O_3 and A^<1+>B^<5+>O_3 through first-principles calculation. As a result, we discovered five oxides NaTaO_3, CaSnO_3, CaTiO_3, CaZrO_3 and BaTiO_3 for the biocompatible lead-free piezoelectric material which have stable tetragonal structure caused by phonon. Stable crystal structures and material properties such as spontaneous polarization and piezoelectric stress constant were analyzed for the five oxides. As a result, NaTaO_3, CaTiO_3 have higher piezoelectricity compared with others.

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Biocompatible piezoelectric materials are becoming increasingly important for actuators and sensors in medical devices such as Bio-MEMS. In this study, a biocompatible piezoelectric MgSiO_3 thin film, which was discovered through first principles calculation, has been fabricated on Cu (111) single crystal substrate by RF magnetron sputtering method. The experimental design method was employed to find an optimum sputtering condition. Then, the crystal structure and the element component of the fabricated MgSiO_3 thin film were analyzed with X-ray Diffraction (XRD) and X-ray Fluorescence Analysis (XRF), respectively. As a result, the fabricated MgSiO_3 thin film was proved to have tetragonal perovskite crystal structure and ideal element component.

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Biocompatible piezoelectric materials are becoming increasingly important for actuators and sensors in medical devices. In this paper, we highlighted on some perovskite-type oxides MgSiO_3, MgTiO_3 CaTiO_3, CaZrO_3 and CaSnO_3 which were discovered through first-principles calculation in our previous studies to fabricate novel lead-free biocompatible piezoelectric materials. In order to verify their biocompatibility, the cytotoxicity of isotopic oxides with the same components was examined as comparing with typical perovskite-type oxides BaTiO_3, LiNbO_3, KNbO_3 and NaNbO_3. The fibroblast (L929) cells were cultured during 7 days and the effect of materials was evaluated by the half maximal inhibitory concentration (IC50). As a result, it was recognized that BaTiO_3, MgSiO_3, CaTiO_3 and CaSnO_3 has the higher biocompatibility. On the other hand, the others has lower biocompatibility. Especially LiNbO_3 and NaNbO_3 shows the strong toxicity.

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In this study the interface effect on the location dependence of the crack growth characteristics by fatigue of an aluminum cast alloy locally reinforced by Al_2O_3 whiskers and SiC particles is studied experimentally. The crack grows normal to the interface between the metal matrix composite (MMC) and the aluminum alloy. The crack growth rate under a constant stress intensity factor range condition showed deceleration with crack growth in MMC. The residual stresses due to casting of the layered material of MMC and aluminum alloy were measured using the strain release method. The deceleration of crack growth rate can be attributed to the compressive residual stress in MMC. The mechanical effect of residual stress on the stress intensity factor of a crack normal to the MMC/aluminum alloy interface is evaluated based on the principle of superposition.

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Free-edge stress singularity usually develops near the intersection of free surface and the interface of bonded dissimilar materials. To defuse the thermal stress that develops due to the difference of the coefficient of thermal expansion, an interlayer may be inserted between two materials. In this study, effects of the interlayer on stress singularity under thermal stress loading were investigated theoretically and numerically. It was found that the free-edge stress singularity disappeared by inserting a proper material into bonded dissimilar materials. The effects of interlayer on the stress distributions was limited in the small area of the order of interlayer thickness around the intersection of the interface and free-surface. Stress distribution calculated by B.E.M. can be normalized by using the exponent of stress singularity, the stress intensity factor and thermoelastic constant stress term of bonded dissimilar materials without an interlayer.

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Free-edge stress singularity usually appears at the intersection of the free-surface and the interface of bonded dissimilar materials. Many researchers studied the free-edge stress singularity of bonded dissimilar materials. Not only isotropic materials but also anisotropic materials such as GFRP are used for making a bonded dissimilar materials. In this study, free-edge stress singularity of bonded dissimilar orthotropic materials with arbitrary principal directions were investigated theoretically by using the characteristic equation deduced in terms of Airy's stress function. Stress distribution on the interface was calculated by using the boundary element method. The value of the exponent of stress singularity determined from the numerically obtained stress distribution agreed well with the theoretical value obtained by using the characteristic equation. It was found that the free-edge stress singularity disappeared for a certain combination of wedge angles

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In this study, fatigue strength of the elastic bonding double lap joint are investigated experimently. It is found that (1) fatigue strength decreases with increasing thickness of adhesive layer. (2) S-N diagram of the elastic bonding double lap joint was approximated to exponential, and the fatigue limit was not observed. (3) the fatigue stress obtained by using circular butt joints is larger than that obtained by using the rectangular lap joint.

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Recently, the bonding technology is used to conclude a lot of structures. As for the glued connection, the point with a high confidentiality in making of the reduction of the decrease of the concentration of stress and the vibration, etc. and products and compact the joint part is paid to attention compared with other joint methods. In this report, Influence of Adhesive thickness, Loading rate and Temperature on strength of Elastic Bonding Joint is examined by static experiment. The shape of the test specimen is double lap shape. As a result, adhesive strength decrease by thinning of the Adhesive layer thickness. Moreover, it decrease with the rise of the temperature(T=25℃). In addition, the rise of the loading rate raises adhesive strength

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Friction-stir-welding (FSW) was performed between aluminum alloy A6061-T6 and cold-rolled steel SPCC-D. The FSWed material was aged again to recover hardness of A6061 side in the joint. Characteristics of the joints were examined on the FSWed material and its aged material in detail. The results showed that no marked defect was formed by FSW and the joints were under good condition. The microstructure near the interface of the FSWed material became very fine and no brittle compound-layer was detected around the interface. The static strength of the FSWed material was maintained at a high level. The static strength reached the same level of A6061 uniform material after aging. Further, Ti-FPB treatment slightly improved the corrosion resistance of the FSW material against salt-water.

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Strength of solder joint with 61.9Sn-38.1Pb lead solder or Sn-3.5Ag-0.75Cu lead free-solder was studied. This study focuses on the effect of loading rate and bonding area on the strength of bonding joint. This experiments have been carried out under biaxial loading at room temperature for both solders. Based on the results, it is found that the bonding strength increases with increasing loading rate, but the effect of bonding surface on the bonding strength are not so large. Comparisons between tensile strength and torsional strength were also discussed

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